Electrical discharge device



Jan. 16, 1934. c. SPAETH I ELECTRICAL DISCHARGE DEVICE Filed 001;. 23, 1930 LMrZea dmefi/ INVENTOR BY KW ATTORNEY srso'rarcsr. nlscnanas nsvrcs Charles Spaeth, Flushing, N. "EL, assignor to Ne-Arga Corporation, Jersey City, N. 3., a corporation of New York application October 23, 1930. Serial No. 490,648

1 Claim. (CL 176-125) This application is a continuation in part of maintain the mercury vaporizing means in opermy copending application Serial No. 343,873, ation at the correct intensity during the entire filed March 2, 1929. g operation of the device. It is, however, possible The invention relates to electrical discharge to start the discharge through the rare gas col- 5 devices, particularly to devices used for purposes umn and then supply the necessary quantity of 0 of illumination. mercury vapor for a short period of time, after It is an object of the present invention to prowhich the device will continue to emit a white vide an electrical discharge tube which is capable light for some time. As operation is continued of producing a very efiicient white light. the mercury is cleaned up, apparently either by 10 Another object is to provide an electrical discondensation, occlusion, absorption, or some 5 charge illuminating tube wherein the color charother phenomena and the light emitted by the acteristics of the emitted light may readily device gradually reverts to the characteristic be modified in a predetermined manner or be color of the rare gas, which, in the case of neon, maintained constant at any desired value. is substantially red. By operating the mercury A further object is the provision of an electrical vaporizing device at the correct intensity, mer- 7 discharge tube operating at high efiiciency and cury vapor is supplied at the same rate at which adapted to produce a concentrated brilliant light it is used up and hence the color of the emitted emission approximating sunlight. light remains constant.

In accordance with my invention a radiant For producing other colors of light other mona- 2 energy emitting discharge device is constructed tomic gases, for example, helium, argon, xenon, 7 having a filling of gas at reduced pressure and a crypton, may be used with mercury vapor, or one plurality of electrodes for conducting an elecof a mixture of the rare gases of a given chartrical discharge therethrough. For modifying acteristic color emission may be used in conjuncthe light emission from the device auxiliary tion with the means for liberating the vapor.

means are arranged to add to the gas filling in the Other objects and advantages and the manner so desired amounts an agent for modifying the radiof attaining them will be made clear in the folation spectrum. This auxiliary device is preferlowing specification and accompanying drawing. ably in the form of a mercury reservoir provided In the drawing, Fig. 1 shows a device constructwith means for liberating mercury vapor. ed in accordance with my invention wherein the A preferred form of my invention for illumimodification of the emitted spectrum is obtained 5 nating purposes comprises an envelope containby the passage of a discharge to a spectrum ing an atmosphere of rare gas, such as neon, and modifying material; and having a reservoir of mercury. Electrodes are Fig. 2 shows a device wherein the cathode is provided for passing a discharge directly through of the oxide coated indirectly heated type.

the rare gas and another electrode for causing 2. Referring more particularly to the drawing, discharge to be passed to the mercury in order to Fig. 1 illustrates an electrical discharge tube comvaporize it. In order to secure the desired charprising a light transmitting envelope 1 filled acteristics of illumination from the device means, with rare gas, such as neon, and having a pair such as resistances, inductances or capacitances of main discharge electrodes 2 and 3 of any well- 40 may be provided for controlling the relative inknown type,-having the usual lead-in wires. The

tensities of the discharges; For liberating the pressure of the gaseous atmospheremay range mercury suitable heating means may be employed anywhere from .1 to 50 millimeters, but I find it in place of the auxiliary electrode. This heating preferable to use apressure in the neighborhood means may comprise any suitable source of exof 6 millimeters. A reservoir for a quantity of 4 ternal heat, but preferably is in the form of a mercury 4 is provided in the form of an appendix 1G9 heating coil placed adjacent to the mercury res- 5. For energizing the tube the main electrodes ervoir and adapted to be energized by the dis- 2 and 3 are connected across a suitable source charge current. of current 14 by means of conductors 6 and 7.

When it is desired to secure a white light ap- The source 13 may be of eitherdirect or alter- 50 proximating that of sunlight the filling of the enhating current of a suitable high potential.

velope may be of neon gas used in conjunction Connected in series with the conductor 6 is an with a reservoir or other means for supplying adjustable resistance 8. For causing discharge an exactly proportioned amount of mercury vato pass to the mercury s a connection 9 is made por. It is advisable where the tube is to be operbetween a lead-in wire 59 sealed through the wall 55 rated over a relatively long period or time to of the reservoir 5 and making contact with the of the gaseous discharge path.

mercury, and the conductor 6. In series with the conductor 9 is an adjustable resistance 10.-

During the construction of the device a quantity of alkali metal is introduced into the tube envelope adjacent to the cathode 3. This alkali metal may, for example, be distilled into the envelope in the well-known manner, so that a film 3 1s formed on the inside of the wall thereof, or a small quantity of it may be put in, in solid form. It is preferable, for best operation, that this deposit of alkali metal form a contact with the cathode 3 or its lead-in wires. The metal used may be sodium, potassium, rubidium, caesium or an alloy of these metals. For commercial purposes potassium may be used alone to save expense. r

This alkali metal is very important to the prolonged operation of the tube as it appears to function as a clean-up agent for excess mercurywithin the main body of the tube. When a tube is used having no alkali metal it turns entirely blue after a relatively short period of operation and can not be restored to its original mercury free color. During the operation of the discharge device a minute amount of mercury vapor is continuously generated by the auxiliary electrode and carried over into the main body of the tube, where it is excited by the main discharge current. When the exciting current is cut off this mercury vapor remains in the main tube and apparently forms an amalgam or other association with the alkali metal, of such character that the mercury is not liberated during future operation of the device. This action is particularly efiective where the alkali metal is electrically connected to the cathode. Without the alkali metal the mercury vapor relatively quickly reaches such density in the main tube that only blue light is generated.

In operation, a current'is caused to pass from.

the source 13 between the two electrodes 2 and 3, thereby energizing the filling of rare gas and causing it to emit light having certain color characteristics. For example, where the rare gas is neon, the light will be predominantly red. In

order to modify these color characteristics the resistance 10 is adjusted so that a discharge passes between the electrode 3 and mercury 4, thereby causing a quantity of the mercury to be vaporized. The-mercury vapor diffuses through the gas in the envelope 1, emitting light rays of .its characteristic blue color. By properly adjusting the resistance 10 it is possible so to balance.

the blue rays emitted againstthe characteristic color of the rare gas as to produce a light emission of any desired color. 'For example, where the rare gas is neon, a proper adjustment of the resistance 10 may be made to cause the emission of white'light, the blue rays of the mercury being complementary to the red rays of the neon. The resistances 8 and 10 serve also as ballast resistances for balancing the negative resistance These resistances should thereforenever be cut entirely out of circuit, as the discharge current would increase to an excessive value. While the mercury reservoir is illustrated as positioned near to one of the main electrodes, it need not necessarily be so located. The device will likewise be operative with the reservoir at other positions. By placing the masses reservoir as shown, the impedance of its dis- I find that a suitable electrode may comprise a thin cylinder 33 of nickel coated with an oxide of barium, strontium or calcium. This cylinder may be heated by a resistance coil 34 energized by a heating transformer 35, the secondary of which is'provided with an adjustable tap 36 by which the neutral point may be determined. A

The desposit of alkali metal 3 is used in this modification the same as in the structure of Fig. 1 and precautions should be taken to prevent the metal from being vaporized by the heat of the cathode and carried out of electrical contact therewith. The lead-in wires 3 and 3, may for example, be made long so as to space the cathode and heater far enough from the alkali metal to prevent vaporization thereof.

It is well known that ordinary light tubes utilizing a filling of rare gas are adapted to operate at only relatively low current densities and that in order to secure life long enough for commercial purposes it has been thought necessary to utilize electrodes operating at relatively low current dencities. A device constructed in accordance with my invention will, on the contrary; operate at extremely high current densities without excessive heating and without excessive deterioration.

Where neon gas and an auxiliary mercury electrode are used, as set forth, the color may be adjusted from the characteristic neon color, through white, to the characteristic mercury color. efliciency of tubes constructed in accordance with my invention is extremely high. For example, when using neon gas with mercury vapor to produce a white light, the amount of energy consumed is only about 0.20 watt per spherical candlepower. Because of this relatively high efliciency the amount of heat generated by the device is correspondingly small.

Lamps of this type are substantially silent in operation, especially when direct current is used. They are therefore of great value wheiea white,

The;

silent and relatively cool, high intensity illuminating source is desired, as in the recording of synchronized sound pictures.

It will be obvious to those skilled in the art that the invention is capable of a wide variety of modifications and adaptations and that the present disclosure is intended merely to illustrate its nature without limiting its scope which is set' forth in the appended claim.

What I claim is:"

An electrical lamp comprising a container, a quantity of rare gas within said container, an anode at one-end of the container and a heater type cathode within and at the other end of said container, a reservoir attached to said container for storing small quantities of mercury, means for vaporizing a quantity of said mercury to modify the color of the light radiated from said rare gas, and a deposit of alkali metal within said container electrically connected to said cathode but spaced therefrom to prevent vaporization by heat generated by the cathode and to remove mercury vapor from the light column.

CHARLES 'SPAETH. 

